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The menace of Long Valley

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The spread of mile-a-minute weed is threatening wildlife and covering swathes of farmland - but officials claim they are powerless to act

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The highly invasive plant Mikania micrantha is smothering the ecologically important Long Valley and threatening bird life because the government lacks the power to eradicate the weed from private property.

The South China Morning Post has also found that Mikania has spread unchecked throughout the city, blanketing many hillsides and mountain slopes, largely because its clearance falls in the bureaucracy gap between governmental departments.

Long Valley is an example of the once-extensive flood plains in the northern New Territories and is effectively the last place where wetland agriculture is practised in Hong Kong. A haven for more than 200 species of migratory birds, Long Valley is often referred to as 'the second Mai Po' by local twitchers and the site has been proposed for eco-tourism.

The plant, commonly referred to as mile-a-minute weed due to its rampant growth, has colonised large tracts of land in the city's second largest freshwater wetland, taking root in abandoned farms and spreading across the valley.

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The noxious weed smothers trees and shrubs in the valley that provide nesting sites for the birds. The weed also threatens the diversity of micro-habitats on which birds depend for sustenance.

'It is impossible to eradicate the weed completely,' said Billy Hau Chi-hang, an assistant professor of the department of ecology and biodiversity at the University of Hong Kong. 'But something can be done to control it at an acceptable level. Its presence in Long Valley is a real concern; many birds may not be able to find suitable nesting.'

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